(d) Only the veins and not the arteries are provided with valves.

(e) Atrial wall is less muscular than the ventricular wall.(f) The arteries are deep seated in the body

Solution –

• The walls of the left ventricle are thicker than the walls of all the chambers.

Answer  – this is so because the left ventricle has to pump blood to the farthest points in the body and also to the brain which is against the gravity .  

• Blood flowing away from the stomach and intestines is put into circulation via the liver and not directly .

Answer – The veins starting from the stomach and intestine first enter liver as a combined hepatic portal vein breaks up into capillaries .

• The blood groups of both the donor and recipient must be known before transfusing blood.

Answer – it is important that the blood groups should be known and they should be matched then only transfusion should be done . This is so because the RBCs contain specific proteins on their surface known as antigens

• Only the veins and not the arteries are provided with valves.

Answer – this is because the veins carry blood from an organ towards the heart . So to prevent backflow of blood they have valves .

• Atrial wall is less muscular than the ventricular wall.

Answer – this is so because the ventricles have to pump the blood top the farthest part of the body .

• The arteries are deep seated in the body.

Answer – Arteries carry oxygenated blood away from the heart to the tissues . The flow of blood in arteries is under high pressure . If they are superficially located then may be they get damaged , so to prevent they are deep seated .